The present invention relates to a drive system for an agricultural large baler.
More particularly, it relates to a drive system for an agricultural large baler which has a rearwardly open bale pressing chamber arranged in a longitudinal direction, a pressing piston movable reciprocatingly in the chamber, devices for lifting harvested product from a field, a transporting passage for collecting an outlet portion of the harvested product and for its transportation into the bale pressing chamber by an additional transporting device, a binding device for binding finally pressed bales, as well as a drive system for driving all operational elements, wherein a drive shaft is located outside of a crank circle of a crank arm for driving the pressing piston.
A large baler of the above mention general type is disclosed in the German patent document DD 299 455. Large balers are usually pulled by field tractors and driven through a hinge shaft connected with a power take-off shaft of the field tractor. For reducing the manufacturing cost as well as for increasing the operational safety and the efficiency, it has been proposed to drive the crank arms for the pressing piston of the main transmission and all shafts for remaining operational elements from a drive shaft located outside the crank circle of the crank arm. The reduction of the input rotary speed of the hinge shaft which is substantially 1000 revolutions per minute does not provide any great rotary speed difference of the output at the drive shaft of the remaining operational elements and on the rotary speed of the crank arm for the pressing piston. For example the drive shaft rotates the remaining operational elements with approximately 200 revolutions per minute and the drive shaft for the crank arm with approximately 60 revolutions per minute. The relatively low rotary speed of the drive shaft of the remaining operational elements has a result that, from the shaft a high torque is transmitted, which makes necessary a corresponding substantial dimensioning of the subsequent transmission and force transmitting means such as shafts, chains, etc.
If this drive system is changed so that the higher rotary speed of the drive shaft of the remaining operational elements rotary speeds are possible, the diameter of the toothed gears in the main transmission changes. As a result, either the additional toothed gear stages are needed or individual toothed gears are so great that they can pass in the corresponding spaces with difficulties. Both features do not correspond to the objective of reduces the manufacturing costs and improving the efficiency. Because of the structural width of the large balers, it is difficult to run all drives from one shaft. In addition, the drive of the binding device must operate substantially synchronous to the drive of the pressing piston, for providing an optimal function without the danger of damages to the binding needle.